1. Field of the Invention
This invention relates to rotary heat exchangers. In one of its aspects, the invention relates to a seal structure for a rotary heat exchanger for use, for example, in incinerators.
2. State of the Prior Art
Incineration of combustible fumes is a problem currently facing many industries such as lithography, smoke houses, paint shops, etc. It has been found that combustion of these fumes at the present time is the most effective way to eliminate the fumes from these industrial processes although the cost of fuel for such incineration has been considerable. Efforts have been made to more completely recoup the heat energy required to raise the fume and air mixture to incineration temperatures. For example, see U.S. Pat. No. 3,706,445 to Charles B. Gentry for FUME INCINERATOR, and U.S. Pat. No. 3,670,667 to William A. Phillips for INCINERATOR WITH EXTENDED HEAT EXCHANGE SURFACE.
It has been proposed to use a rotary heat exchanger to recover the heat from hot exhaust gases for preheating the fume containing gases which are to be incinerated. In such incinerators, the rotating heat exchanger wheel must be sealed in order to prevent appreciable fume containing gases from entering the exhaust without passing through the incinerator.
Rotary regenerators have been used for many years for recouperating heat from hot gases. In recent years, special ceramic materials have been developed for use in these rotary regenerators. The ceramic materials have a very low coefficient of expansion and find particular utility in the automotive field in connection with turbine engines. An example of such ceramic material is Cer-Vit material which is manufactured and sold by Owens-Illinois of Toledo, Ohio.
One of the problems with these rotary heat exchangers has been the inability to effectively seal the edges of the wheel without appreciable frictional resistance. One seal system is disclosed in U.S. Pat. No. 3,372,735 to Meijer. This patent discloses a rotary ceramic heat exchanger for hot gas engines wherein the ceramic heat exchanger wheel has a surrounding ceramic housing which is made from the same type of ceramic material. A gap seal is formed between the movable wheel and the housing. This type of heat exchanger requires precise machining of parts so that the gap forming the seal is very small.
Other rotary regenerators of the metallic type use rubbing seals as disclosed in the U.S. Pat. to Wahlbeck No. 3,389,745. Such seals are subject to wear and develop frictional resistance to rotation of the heat exchanger.